Mechanism of Spontaneous Heating of Hay Part 1 — Necessary Conditions and Heat Generation from Chemical Reactions

The necessary conditions of chemical reactions, occurring following plant respiration and microorganism metabolism in the spontaneous heating of hay, as well as its temperature variations and gas yields were investigated in an adiabatic reactor. The full process of spontaneous heating of hay was successfully demonstrated. Experimental results showed that chemical reactions took place in hay in moist air at temperatures higher than 70° C. The reaction rate increased with the increase of air temperature and relative humidity. Carbon monoxide and carbon dioxide had a production rate of 7.2 ¥ 10–8 (kg/s)/kg-hay and 1.3 ¥ 10–6 (kg/s)/kg-hay at 200° C, respectively. The spontaneous heating of dried hay had two stages, corresponding to moisture absorption and water evaporation, to reach the ignition temperature.